Bulletin d’avalanche

Purcells

Jan 26 – 27, 2015Avalanche Canada
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Archivé · expiré 12 years ago

Danger d’avalanche

Wed
Thu
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
3 · Marqué
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Points saillants

The BC interior is experiencing record warm temperatures. Conservative decision making is recommended until conditions cool off.

Problèmes avalancheux

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    2–5
    A layer of weak surface hoar siting on a crust is buried by 20 to 50 cm of snow.  I anticipate that natural avalanches will remain possible and human triggered avalanche likely as this layer adjusts to the warm temperatures

  • Loose Wet

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1–3
    Warm temperatures will increase the likelihood of loose wet avalanches on steep slopes at lower elevations and alpine features exposed to the sun.

  • Deep Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Unlikely - Possible
    Taille
    3–6
    A deeper layer of surface hoar is still producing the occasional large avalanche. It is especially a concern on open slopes around treeline.  Small avalanches or cornice collapse could step down to this layer increasing the consequences.

Confidence

Good - Freezing levels are uncertain

Weather Forecast

A cold front will start to push the record breaking warm temperatures out of the interior by Tuesday afternoon.  Freezing levels are expected to return to valley bottom early Wednesday afternoon. The region may see isolated flurries and/or showers in the wake of the front. Winds will be light to moderate from the southwest.

Avalanche Summary

We are still in a complex avalanche scenario where touchy conditions are likely to persist. A snowpack with several critical avalanche layers has been stressed first by new load and now by record breaking warm temperatures.  This is resulting in a prolonged and widespread avalanche cycle.  Until we see a cooling in temperatures I anticipate that large natural avalanches will remain possible and human triggered avalanche likely as the upper snowpack continues to adjust.  The mid-January surface hoar layer has been responsible for the majority of the recent avalanche activity, however, I suspect that a large enough trigger in the right spot could have the potential to wake up the deeper mid-December surface hoar especially in open terrain at treeline.

Snowpack Summary

The upper snow pack is settling rapidly and moist snow can be found at the surface on all aspects and elevations.  The depth of the weak layer of surface hoar and crust buried in mid-January is highly variable across the region but in most places can be found between 20 and 40 cm below the surface. It remains my greatest concern.  The mid-December surface hoar layer lies below a strong mid-pack down 60 to 120cm and appears to be gaining strength.    The mid-November weak layer of crusts and facets can still be found near the bottom of the snowpack and has lately been unreactive.

Régions couvertes